34 



MORPHOLOGY 



immediately upon damp earth, but if under water, they form a double 

 wall and become resting spores. When the aerial portion of the plant 

 is exposed to drought, the contents retreat into the protected rhizoidal 



branches and round off into a 

 large number of non-motile 

 spores (aplanos pores), which rest 

 until the return of favorable con- 

 ditions and then initiate new 

 plants (fig. 93). The develop- 

 ment of aplanospores is common 

 among algae, being a method 

 used by the protoplast of bridg- 

 ing over unfavorable conditions, 

 in which connection it appears 

 more as a method of self- 

 preservation than of reproduc- 

 tion. The aplanospores in ger- 

 mination give rise to new plants 

 directly or to zoospores. 



The testimony in reference to the 

 sexual reproduction of Botrydium is 

 conflicting. It has been stated that 

 the aplanospores give rise to numer- 

 ous small biciliate gametes that con- 

 jugate, but it is claimed that the 

 gametes observed are those of Proto- 

 siphon, a form which grows with 

 Botrydium and closely resembles it. 

 In any event, the presence of gametes 

 among these simpler Siphonales is the 

 important point for our purpose, and 



* is of interest to note that 



92 



FIGS. 90-93. Botrydium: 90, the ordi- 

 nary vegetative form, showing the aerial green either conjugate or germinate as small 

 portion and the subterranean rhizoidal portion zoospores. 



^r^^rsrfrt^ vaucheria - - s * the ? 



spores ; 93, the formation of aplanospores in Common green felt, which OCCUrS 

 the rhizoidal % region. After ROSTAFINSKI and j n coarse feltlike masses of 



branching filaments on damp 



soil and in fresh or brackish water (fig. 94). As in all coenocytic 

 bodies, the nuclei and chloroplasts are numerous, and in this form oil- 

 globules are abundant 



